It was narrated that Anas bin Malik said: "The Messenger of Allah used to perform ablution for every prayer, and we used to perform all of the prayers with one ablution."

Sulaiman bin Buraidah narrated from his father that: The Prophet used to perform ablution for every prayer, but on the day of the conquest of Makkah, he performed all of the prayers with one ablution.

Fadl bin Mubashshir said: "I saw Jabir bin 'Abdullah performing every prayer with one ablution, and I said: 'What is this?' He said: 'I saw the Messenger of Allah doing this, and I am doing as the Messenger of Allah did.'"

It was narrated that Abu Ghutaif Al-Hudhali said: "I was listening to 'Abdullah bin 'Umar bin Khattab in the mosque, and when the time for prayer came, he got up, performed ablution, and offered prayer, then he went back to where he had been sitting. When the time for 'Asr (Afternnon prayer) came, he got up, performed ablution, and offered prayer, then he went back to where he had been sitting. When the time for Maghrib (Sunset prayer) came, he got up, performed ablution, and offered prayer, then he went back to where he had been sitting. I said: 'May Allah improve you (i.e., your condition) Is it obligatory or Sunnah to perform ablution for every prayer?' He said: 'Did you notice that?' I said: 'Yes.' He said: 'No (it is not obligatory). If I perform ablution for Morning prayer I can perform all of the prayers with this ablution, so as long as I do not get impure. But I heard the Messenger of Allah say: "Whoever performs ablution while he is pure, he will have ten merits." So I wanted to earn the merits.'"

'Abbad bin Tamim narrated that his paternal uncle said: "A complaint was made to the Prophet about a man who sensed something (some doubt about his ablution) during prayer. He said: 'No (he does not have to perform ablution) unless he notices a smell or hears a sound.'"

It was narrated that Abu Sa'eed Al-Khudri said: "The Prophet was asked about doubts (concerning ablution) during prayer. He said: 'he should not leave until he hears a sound or detects an odor.'"

It was narrated that Abu Hurairah said: "The Messenger of Allah said: 'No ablution (is needed) unless there is an odor or a sound.'"

It was narrated that 'Amr bin 'Ata' said: "I saw Sa'ib bin Yazid sniffing his garment, and I said: 'Why (are you doing) that?' He said: 'I heard the Messenger of Allah say: "No ablution (is needed) unless there is an odor or a sound."

It was narrated from 'Ubaidullah bin 'Abdullah bin 'Umar that his father said: "I heard the Messenger of Allah being asked about water in the wilderness that is frequented by beasts and predators. The Messenger of Allah said: "If the water reaches the amount of two Qullah, nothing can make it impure (Najis).'" (Sahih) Another chain with similar wording.

A similar hadith is narrated through this chain as well.